Method and apparatus for preventing over-shifting on electric vehicles

Abstract

Methods and apparatus are provided for preventing over-shifting in electric vehicles having a multi-gear transmission and an electric motor operable in a drive mode and a regenerative braking mode. The method includes: (a) predicting the speed of the electric motor resulting from downshifting from a current gear being used to a next lower gear based on a current speed of the electric vehicle, a current speed of the electric motor, and a gear ratio of the next lower gear; (b) determining if the speed of the electric motor predicted in (a) will cause an overvoltage condition from regenerative braking or an overspin condition in the electric motor; (c) preventing downshifting to the next lower gear when it is determined that the downshifting will cause an overvoltage condition or an overspin condition in the electric motor; and (d) repeating steps (a), (b), and (c) a plurality of times.

What is claimed is: 
     
       1. A method of preventing over-shifting in an electric vehicle having a multi-gear transmission and an electric motor operable in a drive mode and a regenerative braking mode, the method comprising the steps of:
 (a) predicting the speed of the electric motor resulting from downshifting from a current gear being used to a next lower gear based on a current speed of the electric vehicle, a current speed of the electric motor, and a gear ratio of the next lower gear; 
 (b) determining if the speed of the electric motor predicted in (a) will cause an overvoltage condition from regenerative braking or an overspin condition in the electric motor; 
 (c) preventing downshifting to the next lower gear when it is determined that the downshifting will cause an overvoltage condition or an overspin condition in the electric motor; and 
 (d) repeating steps (a), (b), and (c) a plurality of times. 
 
     
     
       2. The method of  claim 1 , further comprising prior to step (a), determining if the multi-gear transmission is in the process of downshifting from the current gear being used to the next lower gear. 
     
     
       3. The method of  claim 2 , wherein determining if the multi-gear transmission is in the process of downshifting is performed using a gear sensor providing analog or linear gear position information. 
     
     
       4. The method of  claim 1 , the method steps are implemented in a vehicle control unit or an engine control unit of the electric vehicle. 
     
     
       5. The method of  claim 1 , wherein step (b) further comprises calculating an output voltage of the electric motor based on the predicted speed of the electric motor and a motor voltage constant. 
     
     
       6. The method of  claim 1 , wherein step (c) comprises energizing an electromagnetic solenoid to prevent movement of a shift lever outside a gear box unit of the multi-gear transmission or to prevent movement of a shift shaft gear inside the gear box unit. 
     
     
       7. The method of  claim 1 , further comprising enabling downshifting to the next lower gear when it is determined that the downshifting will not cause an overvoltage condition or an overspin condition in the electric motor. 
     
     
       8. The method of  claim 1 , wherein the electric vehicle comprises an electric motorcycle, an electric tricycle, or an electric all-terrain vehicle. 
     
     
       9. An electric vehicle, comprising:
 an electric motor operable in a drive mode and a regenerative braking mode; 
 at least one drive wheel; 
 a multi-gear transmission connected to the electric motor and the at least one drive wheel for transmitting torque therebetween; 
 an energy storage system for providing power to the electric motor in the drive mode and being rechargeable by the electric motor in the regenerative braking mode; 
 a downshifting prevention apparatus; and 
 a vehicle control unit to prevent over-shifting in the electric vehicle, the vehicle control unit configured to: 
 (a) predict the speed of the electric motor resulting from downshifting from a current gear being used to a next lower gear based on a current speed of the electric vehicle, a current speed of the electric motor, and a gear ratio of the next lower gear; 
 (b) determine if the speed of the electric motor predicted in (a) will cause an overvoltage condition from regenerative braking or an overspin condition in the electric motor; 
 (c) actuate the downshifting prevention apparatus to prevent downshifting when the vehicle control unit determines that downshifting to the next lower gear will cause an overvoltage condition or an overspin condition in the electric motor; and 
 (d) repeat (a), (b), and (c) a plurality of times. 
 
     
     
       10. The electric vehicle of  claim 9 , further comprising a motor controller for controlling operation of the electric motor and a throttle coupled to the motor controller for regulating speed of the electric vehicle. 
     
     
       11. The electric vehicle of  claim 9 , further comprising a gear sensor providing analog or linear gear position information for determining if the multi-gear transmission is in the process of downshifting from the current gear being used to the next lower gear. 
     
     
       12. The electric vehicle of  claim 9 , wherein the vehicle control unit is further configured to calculate an output voltage of the electric motor based on the predicted speed of the electric motor and a motor voltage constant. 
     
     
       13. The electric vehicle of  claim 9 , wherein the downshifting prevention apparatus comprises a mechanism to prevent movement of a shift lever outside a gear box unit of the multi-gear transmission. 
     
     
       14. The electric vehicle of  claim 13 , wherein the mechanism to prevent movement comprises an electromagnetic solenoid having an extendable piston for restricting movement of the shift lever. 
     
     
       15. The electric vehicle of  claim 9 , wherein the downshifting prevention apparatus comprises a mechanism to engage a shift lock to prevent movement of a shift shaft gear inside a gear box unit of the multi-gear transmission. 
     
     
       16. The electric vehicle of  claim 15 , wherein the mechanism to engage a shift lock comprises an electromagnetic solenoid having an extendable piston. 
     
     
       17. The electric vehicle of  claim 9 , wherein the vehicle control unit is further configured to enable downshifting to the next lower gear when it determines that the downshifting will not cause an overvoltage condition or an overspin condition in the electric motor. 
     
     
       18. The electric vehicle of  claim 9 , wherein the electric vehicle comprises an electric motorcycle, an electric tricycle, or an electric all-terrain vehicle.